Disappointing. I share your frustration with situations like that where identifying at genus (or even subgenus) level doesn’t really seem an adequate solution because we can exclude most species in the genus.
I’m not a bumblebee expert (or even any good at identifying them), however I know that in the UK there are four species which are difficult/impossible to tell apart visually (for the workers at least). There is Buff-tailed Bumble Bee (Bombus terrestris) plus the White-tailed (Bombus lucorum) complex which includes Bombus lucorum, the Cryptic bumblebee (Bombus cryptarum) and the Northern white-tailed bumblebee (Bombus magnus). This complex is recognised but I don’t think it’s monophyletic based on the this phylogenetic tree so I don’t think it can be added to iNaturalist.
There are over 5000 observations of B. terrestris, 1500 of B. lucorum, 141 B. cryptarum & 14 B. magnus. I’m guessing some are incorrectly identified and some are identified at genus/subgenus level when they are clearly one of these 4 species.
Personally I like the idea proposed by silversea_starsong:
I know we can just enter “subgenus bombus” with a comment explaining that it could be any of 3 species but doing it this way could allow searches etc.